Combi Boilers Significantly Increase Apartments’ Energy Efficiency

Complex transitions to 151 individual boilers with virtually no downtime

In 2012, Meadowbrook Gardens, a 10-building, 151-unit apartment complex in Parsippany, N.J., underwent an extensive renovation, including upgrades to heating and hot-water systems. The goal of The InterGroup Corp., the Los Angeles-based owner of the complex, was to individualize utilities for each unit and increase overall energy efficiency.

At the time, each building had a centrally located 1-million-Btu hot-water boiler that provided space and water heating for all units. In addition to being inefficient, the large floor-mounted boilers occasionally would be threatened by standing water caused by flooding of a nearby creek. To address these problems, InterGroup hired Beta American Services of Oakland, N.J. The contractor recommended replacing the hot-water boilers with smaller and more efficient wall-mounted condensing boilers—one for each unit. With the property owner’s approval, the contractor began researching different high-efficiency combination, or combi, boiler models.

“Combi” is a European term used to describe a compact boiler containing both an open-loop domestic-hot-water output and a closed-loop central heating output.

“Before the Rinnai presentation, another brand of boiler was specified for the retrofit, but based on the project’s Btu needs, the Rinnai unit was clearly the best choice,” Pete Monahan, owner of Beta American Services, said. “The original spec was for a 200,000-Btu unit, and the heat-load limit for the apartments was significantly lower, so the Rinnai boiler was a better fit in regards to sizing and modulation range, and it has a great heat exchanger. If we’d installed the higher-Btu boiler, it would not have modulated very well, essentially staying in fixed low fire the whole time, instead of being used to its intended capacity.”

The E75CN is a 75,000-Btu, highly efficient boiler designed for homes and apartments with smaller domestic-hot-water requirements—one to two baths. This made it an excellent fit for Meadowbrook Gardens, which offers one- and two-bedroom floor plans—750 and 900 sq ft, respectively—each with one bathroom.

A combi boiler, the E75CN uses an integrated single-speed boiler pump, expansion tank, and three-way valve that provides domestic priority and supplies both heat and continuous hot water. The boiler also comes with a factory-assembled low-loss-header plumbing kit.

The first order of business was developing a way to reduce installation costs for the budget-conscious property owner.

“They wanted the up-front cost to be as low as possible, so we had to figure out a way to get 151 of these boilers properly installed and vented very quickly,” Monahan said. “We developed a plan to build the boiler assemblies off site in our shop, mount them on painted plywood, and transport them to the job site virtually ready for installation.”

Beta American Services developed a schematic for the boiler assembly and then built one to serve as a template. The team recorded every dimension, cut, and piece needed; created an AutoCAD drawing of the assembly; and numbered every component that accompanied the boiler. Then, it made and stocked storage bins for each component and built six work stations for the fabrications.

“After getting over the learning curve, the guys at each work station were eventually able to fabricate four boiler packages a day,” Monahan said. “We’d wait until we got a full load and then take them to the job site and mount all the boilers for a building. And we set it up so there would be only minimal downtime for the tenants. We had to do a lot of planning ahead of time to make it all work, but it ended up going very smoothly.”

The basements of the apartment buildings offered ample wall space. The contractor’s crew mounted the boiler panels on the walls and readied all of the piping, setting the stage for quick transfer once the old boilers were shut down. The crew then coordinated with the local gas utility for the installation and inspection of gas meters for each unit. With these steps completed, the crew was able to finish connecting the boilers to the fixtures of each apartment.

With its efficient installation method, the crew was able to transfer to the new heating and hot-water system with almost no downtime. This was critical, as the project took place during fall and winter.

“Beta American Services clearly did their due diligence before they even attempted the job instead of just going in and installing a bunch of boilers,” David Vaccari of Advanced Hydronics said. “They had a great plan in place, and that saved significant time and labor costs.”

Advanced Hydronics provided technical support throughout the project and trained Meadowbrook Gardens’ staff on proper operation and maintenance of the new equipment. The project ran smoothly and was finished during the first quarter of 2013. According to Monahan, the energy savings have been remarkable.

“With the old hot-water boilers, the property owner was paying up to $40,000 a month for gas,” Monahan said. “Not long after we installed the boilers, the manager of the complex told me that some of the tenants were saying that their new monthly gas bills were between $40 and $60. So, with 151 apartments, that would be a total of less than $10,000 a month. Those are pretty significant savings.”

Monahan saved the template from the Meadowbrook Gardens project and plans to use it for future projects requiring multiple boilers.

“The low-loss headers of the Rinnai boilers certainly helped us save some time, and the system went together very smoothly,” Monahan said. “I also like that the boilers have a plastic jacket, as opposed to a metal jacket, for corrosion resistance, especially when we’re working in high-humidity areas. They won’t rust, and they’re easy to clean.”